1. Technical Field of the Invention
The present invention relates to novel insoluble s-triazine compounds bearing benzalmalonate and/or phenylcyanoacrylate substituents, to a process for the preparation thereof and to the use of same in particulate form as UV screening agents, in particular in the cosmetics field.
The present invention also relates to the use of such novel compounds for photoprotecting the skin and/or the hair against ultraviolet radiation, or for photoprotecting any other UV sensitive material or substrate (inorganic or organic glasses, plastics or the like).
2. Description of the Prior Art
It is known to this art that light radiation of wavelengths of from 280 nm to 400 nm promotes tanning of the human epidermis, and that light rays of wavelengths from 280 nm to 320 nm, i.e., UV-B irradiation, cause skin burns and erythema which may be harmful to the development of a natural tan; such UV-B radiation should thus be screened from the skin.
It is also known to this art that UV-A radiation, of wavelengths of from 320 nm to 400 nm, which causes tanning of the skin, is prone to induce an adverse change therein, especially in the case of sensitive skin or of skin which is continually exposed to solar radiation. UV-A irradiation causes, in particular, a loss in the elasticity of the skin and the appearance of wrinkles, promoting premature skin aging. Such irradiation promotes triggering of the erythemal reaction or amplifies this reaction in certain individuals and may even be the source of phototoxic or photoallergic reactions. Thus, it is desirable to also screen out UV-A radiation.
A wide variety of compounds useful as sunscreens, essentially in the form of soluble organic screening agents or insoluble inorganic compounds, are known to this art. These screening agents must be able to absorb or block the harmful rays of the sun, while at the same time remaining harmless to the user.
In this respect, and to limit the possible risks of allergy on the skin generated by organic screening agents on account of their solubility, inorganic pigments such as zinc oxide or titanium dioxide are increasingly used to screen out UV irradiation. However, these inorganic pigments present the drawback of being sensitive to solar radiation (phenomenon known as "photobluing"). Moreover, for equivalent amounts, these inorganic pigments are less effective in UV protection than the aforesaid organic screening agents.